and this new study suggests that about a flu, during a pregnancy, can increase a child's risk. abc's chief medical editor dr. richard besser here with the whole picture. so many pregnant couples are going to be in fear. what do you want to say to them? >> reporter: well, what the study found was that moms who remembered having the flu during pregnancy, the risk of having an autistic child doubled, it went from 1% up to 2%. still very, very small. and this type of study is called an exploratory study. so, it doesn't prove anything, but it says, hey, we need to look at this further. >> let's look at the other risk factors we've heard about over time. where does this rank with them? >> reporter: well, you know, it's along the same level. we have some clues. genetic factors are important. we know that autism runs in families. more common in boys. those point to genetics. parents age matters, as fathers in particular get older and hit 40, the risk goes up. and then spacing between pregnancies. if you have children closer than every three years, the risk goes up, too. lots of clues, no hard answers.